FWD vs RWD: Adders, Subtractors, and Weight, Oh my...!

[dj10]

Since most cars can't to to the weights that are mentioned are you willing to add to weight to all the rwd cars? Another thing I didn't see mentioned was the lenght of the races we run. How much extra advantage do you need when all of the sprint races are less than 45 minutes?
I saw a RSX run 1.42.4 (Good Driver) (track record was 1.43.5) @ Mid Ohio last race of the year, sure he got dq'ed for being 19# under weight and I ran 1.43.3 with a full tank of fuel (I always try and test something at the wrong times):~). Let's wait and see some how these fwd car are develop this year and don't jump to conclusions just yet.

 

[Duc]

produces much more whp then it is rated at the flywheel from the factory

They all play games with the "Advertised" hp numbers through the years. That is why the SAE produced a certifiable standard(which is better than nothing). And if they are understated then yes the 25% number "may" work. Also you can make any vehicle make high gains (Dyno queens) but how long is it going to last?

I guess my point is that with the more modern vehicles and designs come more modern systems (EFI, Exhaust, Cooling, Intake, Valvetrain). Those systems are under tighter control to squeeze out the last amount of performance, be it WHP, Fuel Economy, Emmissions, or Reliability. Think of it as a box with each one in a corner. The design of the motor is looking to hit a defined target for that market. So if you take a motor designed for Fuel Economy, Emmissions, or Reliability and slide it to the performance corner larger gains will be realized. But if you already have a system designed for performance (usually with a touch of emmissions and reliability) the gains will not be as large (10-18)%.

Many of the Celica owners have found simple ported stock headers to be a best bet on a NA motor. I find a 25% gain on a 2zz-ge to be absurd (and I am fine with that). I am sure there are other examples out there that have the same issues.

 

[Knestis]

Duc describes what I *think* consideration of a displacement-specific power value should theoretically overcome (in the parallel thread).

But you know what? If nobody but me is worried about these issues, maybe I should set them free. Remember Greg A's point that we WILL eventually get "the IT that we ask for."

K

 

[Chip42]

blanket statements aside - the point is that many of the (yes, often over-rated by the factory) small displacement / high output motors won't see 25% gains over factory spec. this makes the "process" broken for those examples. as ITR FWD cars started this thread, we need only focus on the 'teg Type-R and Celica GTS for relevant and known examples. these are pretty built-to-the hilt motors from the factory, and are documented to NOT see the gains presumed. RENESIS (13B evo) motors don't, either. ask anyone who WAS thinking about building an ITR RX-8.

adding weight to the RWD cars might work. it might not. as weight is really the only tool I know of available to the ITAC to try and make parity, it's the item we have chosen to discuss. Most of these discussions center around reducing weights, I was just pointing out that adding is often much more feasible. and if we look at the numbers, we MAY find that fewer rules changes would result by adding weight to some cars than subtracting it from many. particularly with the recent chanegs to the cage rules minimum wall thickness that have made a lot of existing cages heavier than they need to be now (if only by a few pounds).

and, as DUC noted, how the mfg achieved their HP ratngs varied widely until the very recent adoption of the SAE certified HP numbers. the likes of honda and toyota used to use dyno-setup calibrations and super-lightwweight oils to achieve their numbers. GM used computer models and estimates. real world numbers show that the "'das" were far OVER rated (thus the removal of the 2zz-ge from the US market) and that the GMs of the world were actually CONSERVATIVE and under rated their actual outputs. Then there is the oft-believed (though I don't have proof either way) notion that some engines (example: B16) were purposely under-rated so as not to detract from the star power of higher-end cars in the stable. obviously, the process cannot account for these variables, but they are worth noting in such a discussion.

and jimmyC - the d-series hondas, in particular the A6, are known to wake up pretty impressively under IT rules. I had no intention of including them in my "blanket". thanks for the numbers, anyhow - they are noteworthy.

 

[Greg Amy]

OK, another mega-post...

My gut reaction...the lower numbers get too much of a break...the higher numbers get too much of a break, yet the middle is closer to ok...

That shouldn't be surprising, Jake; given I was offering a simplistic linear example, I intentionally used the middle as...well, the middle.

You want it to ramp faster at the bottom, the top, or both? How about another simplistic example, using exponents? This one starts fast then asymptotes up to a near flat value:

x=1.85^y

x = weight, before subtractor, in thousands
y = subtractor, in hundreds

Results in:

Weight/subtractor:
1950/100
2230/120
2390/130
2550/140
2730/150
2910/160
3110/170

...and so on.

whats interesting to me, is that some of the ITAC were not to long ago saying that the "within 100lbs of the proccess weight is fine."

I'm sincerely hoping this is being addressed adequately to zero, or at the minimum something that is truly insignificant, like 10#. Without that corrected, all of our "formulas" are just 'rearranging the deck chairs".

...cars...in ITS and ITR...really couldn't even benifit for a lower minimum weight, as almost all of them struggle to make it to their current minimum weights...There is no way your are getting a DC integra Below 2500lbs.

You'd be surprised. Dick Patullo showed us this year what's possible if you really, really try. And my (limited) experience says we've got room to...shrink?

Besides, unless the classified number is stupid low, I'd personally rather work to get a car light and end up fighting a bit heavy in a faster class, than try to fight an uphill battle with a heavier car in a slower class. Especially a FWD car.

"Not thinking it can attain that weight" is not an acceptable decision to make on the rulesmaker level. It's the same - can I call it "arrogant"? - position as stating "well, no one's ever built one, but we think it's OK". You can't say that and then from the other side state "well, we're not going to make any adjustments until you build one and prove it can/can't be done".

personally - I think the adder for RWD is becoming more the place to go.

Problem is, it'll never fly. It would mean a wholesale change to all cars in all categories, and that'll never get approved. Further, it's a different mindset: it does not address "handicapped" cars with a break, it handicaps all cars instead.

Jake Gulick: IF I were king, I'd think it could be simple, like:

That's fine, but, like the example you cited above, it only addresses the middle and not the outliers. Any wonder why the CRX Si (among others) is so dominating at its "pre adjustment" weight and doesn't seem to fit the process? Simple: because of its lower horsepower it does not approach the edges of tire capability as compared to the heavier cars within ITA. Given a weight formula severely biased towards difference in horsepower (almost to an exclusion, when compared to total weight), a single-hit FWD subtractor isn't enough on such a light car to surpass the level where FWD is a detriment.

Bottom line: a one-size-fits-all approach does not work in the real world. It will always be optimized for the middle and never effectively cover the outliers. After all this, you still want to go with hard, flat, one-hit numbers for the entire class, then you must accept that it will fail at the ends of the spectrum within each class...

GA

 

[lateapex911]

That's fine, but, like the example you cited above, it only addresses the middle and not the outliers. Any wonder why the CRX Si (among others) is so dominating at its "pre adjustment" weight and doesn't seem to fit the process?

GA

It's dominance might also have to do with:-
-Under rated factory hp
- it's a popular car before being classed, and it's mistakenly low initial weight leads to more folks racing it which leads to more data, which leads to more speed...

 

[Chip42]

Problem is, it'll never fly. It would mean a wholesale change to all cars in all categories, and that'll never get approved. Further, it's a different mindset: it does not address "handicapped" cars with a break, it handicaps all cars instead.

not really - we have been talking about a change to "the process" and a change to the classification weight of FWD cars in the first place. why not do the same, and make it a BETTER process that nay subtract or may add weight, but with the objective of establishing parity on a relaistic weight scale?

We would obviously have to come up with a formula that is GOOD, accounts for those known outliers like the CRX you site, without harming the FWD cars with opressively high weights nor out-of-reach low weights. it would need to account for drivetrain and suspension shortcomings (struts/live axle/FWD/etc..) with something other than a fixed adder, and address the power/displacement issue so that high-strung cars are calculated with a realistic expected HP, simillarly for the cars that fit the current expectations - a set 20-25% gain is not realistic in all cases. obviously there will always be examples of cars that will blow any good formula on one side or the other, but competition adjustments OVER TIME, such as the weight added to the ITA CRX Si a few years ago, can rectify those places where it is obvious that the formula has failed us.

this won't mean, necessarily, a wholesale reweighing of the class, but I'm sure some of the established cars might gain a few, and a lot of the ITR cars would change.

my $0.02, and I'm working on developing such a formula...

 

[ekim952522000]

..........

Weight/subtractor:
1950/100
2230/120
2390/130
2550/140
2730/150
2910/160
3110/170

...and so on.


...........

Greg did the idea I posted about using a modified PW/WT ratio for FWD cars in ITR of 10.45ish not fit the goal you were going for? Just curious there really has not been any comments on it.

 

[Greg Amy]

Greg did the idea I posted about using a modified PW/WT ratio for FWD cars in ITR of 10.45ish not fit the goal you were going for? Just curious there really has not been any comments on it.

Sorry, didn't mean to ignore it; there were just a lot of different ideas here (I'm reading them all) and I only chose to hit the highlights.

Your idea, in effect, is to use a different multiplier for FWD cars (if you back-calc'd what you're offering to do, it's as simple as instead of taking the 1.25 standard multiplier, making it something smaller.) This idea certainly has merit; after all, my whole premise is no different, other than I'm calculating the "subtractor" afterward instead of beforehand.

The only concern I have with such an idea is that it's a fairly radical departure from current practice. knowing the history of The Great Realignment", I'm loathe to offer such large departures from the norm; I suspect that many, if not most, ITAC and CRB members are still suspicious of the whole idea(l). On the other hand, convincing them to simply twiddle around with only one of the post-calc adders/subtractors is probably a far more attainable goal.

If the ITAC would be interested in entertaining such a thought, in lieu of doing a subtractor afterwards (and thus coming to a similar, if not exact, result) I think it's worth consideration. - GA

 

[ekim952522000]

Sorry, didn't mean to ignore it; there were just a lot of different ideas here (I'm reading them all) and I only chose to hit the highlights.

Your idea, in effect, is to use a different multiplier for FWD cars (if you back-calc'd what you're offering to do, it's as simple as instead of taking the 1.25 standard multiplier, making it something smaller.) This idea certainly has merit; after all, my whole premise is no different, other than I'm calculating the "subtractor" afterward instead of beforehand.

The only concern I have with such an idea is that it's a fairly radical departure from current practice. knowing the history of The Great Realignment", I'm loathe to offer such large departures from the norm; I suspect that many, if not most, ITAC and CRB members are still suspicious of the whole idea(l). On the other hand, convincing them to simply twiddle around with only one of the post-calc adders/subtractors is probably a far more attainable goal.

If the ITAC would be interested in entertaining such a thought, in lieu of doing a subtractor afterwards (and thus coming to a similar, if not exact, result) I think it's worth consideration. - GA

If we are were to do something like you suggest I think something like a modified pw/wt ratio is simplier than using a whole bunch of different subtractors, even thought they very likely would have the same result. Basically it would be like saying the power to weight ratio for FWD drives in ITR is 10.75 and 11.25 for RWD.

See below as the cars get more powerful/heavier they get more of a weight break. the 10.75 is obviously just a guess but as you can see with this example the Celica (180) would get a 113lb deduct and the acura legend (230) would get a 144lb deduct. but I guess the problem with it is that it is still linear.......




-------X1.25- X11.25- X10.75
Stock- IT HP- RWD -FWD- DIFF
180 225 2531 2419 113
190 238 2672 2553 119
200 250 2813 2688 125
210 263 2953 2822 131
220 275 3094 2956 138
230 288 3234 3091 144
240 300 3375 3225 150
250 313 3516 3359 156
260 325 3656 3494 163
270 338 3797 3628 169
280 350 3938 3763 175

 

[Knestis]

>> If the ITAC would be interested in entertaining such a thought, in lieu of doing a subtractor afterwards (and thus coming to a similar, if not exact, result) I think it's worth consideration.

I'm not quite completely out of steam on these ideas. It would help if we had a concrete suggestion for a function describing an actual curve, that provided a factor we could use in lieu of the big chunk adders. I *think* that if it accommodates the existing cases thought of as benchmarks, spitting out weights that are close enough to not cause any giant heartburn, it's got potential - simply as an exercise in selling policy.

EDIT - Mike's table might be the basis for defining just such math.

K

 

[lateapex911]

Mike, it might be linear, but it's "self adjusting from class to class...so thats a good thing.

And, similar to choosing a "bogey weight" for the middle of the class, like 100 pounds for ITA then modifying the weight via a percentage, this does it in one step.

 

[ekim952522000]

Mike, it might be linear, but it's "self adjusting from class to class...so thats a good thing.

And, similar to choosing a "bogey weight" for the middle of the class, like 100 pounds for ITA then modifying the weight via a percentage, this does it in one step.

Here is a spread sheet were you can play around with different FWD pw/wt ratios and the difference it makes compared to RWD cars with 4 example cars on the left.

The sheet is setup for ITR with the "Bogey" being the Celica assuming a 100lb deduct for it is correct.

http://www.westcoasthc.com/FWD.xls

 

[ekim952522000]

Ok I just spent about a hour running simulations through Bosch LapSim. Here are the results.

The only things I changed on the cars were FWD or RWD, HP and weight, and weight balance I used 60/40 for all the FWD tests and 50/50 for all the RWD tests.

The results are interesting.

 

[Greg Amy]

Shocking results...

 

[Knestis]

The trends does indeed suggest that what we generally thought to be the case. At what lower HP point does it indeed seem to "not matter" anymore? I'd like to test the hypothesis that we can set this one free for low-HP cars...

K

 

[Greg Amy]

At what lower HP point does it indeed seem to "not matter" anymore?

Do note that the above assumes the actual engine output; ergo, reduce the power numbers appropriately to account for IT build. In other words, where it says 150 hp above, that's generally going to mean 120 stock hp (assuming 25% power increase).

My guess? FWD no longer becomes a factor around 100-ish hp, as long as the classified weight is also small; i.e., ITC territory. And, it really starts to make a difference around 150/160-ish stock hp.

You guys don't need LapSim, you've got tGA <HEEE-UGE wink and a grin>.

GA

 

[Andy Bettencourt]

Do note that the above assumes the actual engine output; ergo, reduce the power numbers appropriately to account for IT build. In other words, where it says 150 hp above, that's generally going to mean 120 stock hp (assuming 25% power increase).

My guess? FWD no longer becomes a factor around 100-ish hp, as long as the classified weight is also small; i.e., ITC territory. And, it really starts to make a difference around 150/160-ish stock hp.

You guys don't need LapSim, you've got tGA <HEEE-UGE wink and a grin>.

GA

I am sure that I am missing something but don't the numbers above show that the HP level DOESN'T matter THAT much? At 2500lbs, as you increase the hp, the delta in lap times stays pretty static...only a .3 difference when you add 50hp from 200 to 250hp?

Seems weight is the major issue. So if you had to choose, wouldn't weight be a better starting point? At least in ITS and ITR where the cars are heavy enough to have this be a factor...

 

[Ron Earp]

You guys don't need LapSim, you've got tGA <HEEE-UGE wink and a grin>.

Sorry for my ignorance but what is LapSim and what is tGA?

Thanks,
Ron

 

[JeffYoung]

How does Lapsim work? What are the inputs? Does it have a built in modifier/handicap for FWD? Why do we consider this statistical significant when the lap time differences even in the high hp range are around a second?

And why are we considering using a simulator when we are already so distrustful of dyno sheets?

I suspect we could use that same simulator, with the appropriate human inputs, to show similar detriments due to poor aero, or brakes, etc. Do we want to go there?